In the completion of oil wells and the like, a bore hole is first formed in the earth. A casing is then installed in the bore hole and is cemented in place, the function of the casing and the cement being to isolate the various strata of the bore hole one from the other. Next, one or more shaped charges is positioned within the casing and is actuated to perforate the casing and the cement, thereby providing communication between the adjacent formation and the interior of the well. If the formation is oil bearing, oil flows from the formation into the well and is thereafter recovered at the surface.
Shaped charges used in perforating oil wells and the like typically comprise a housing which is cylindrical in shape and which is formed from metal, plastic, rubber, etc. The housing has an open end and receives an explosive material having a concave surface facing the open end of the housing. The concave surface of the explosive material is covered by a liner which functions to close the open end of the housing.
When the explosive material is detonated, a compressive shock wave is generated which collapses the liner. The inner portion of the liner is extruded into a narrow diameter high-speed jet which perforates the casing and the surrounding cement comprising the oil well, etc. The remainder at the liner can form a larger diameter slug which can follow the high-speed jet into the perforation, thereby partially or completely blocking the perforation and impeding the flow of oil there through.
Heretofore, numerous attempts have been made to solve the problems of slugs of liner material interfering with the successful completion of oil wells, etc. For example, liners for shaped charges have been formed from various materials by forming the materials into powders and then pressing the powdered materials into the desired liner shape. Liners comprising compressed powdered materials are very fragile and therefore tend to disintegrate into very small pieces when the shaped charge assembly is actuated. However, liners formed from pressed powdered materials, either sintered or unsintered, tend to be either porous or hydroscopic, or both, and therefore do not provide adequate protection for the explosive material comprising the shaped charge.
Another approach to the problem of slugs of liner material interfering with well completion comprises the use of liners formed from materials having a discrete second phase. The second phase of such materials is selected either to be molten at operating temperatures or to be brittle. In either case, liners formed from such materials are intended to pulverize upon actuation of the explosive material comprising the shaped charge assembly thereby preventing the formation of a slug of liner material. Shaped charge liners of the discrete second phase type have been successful in operation.
The present invention comprises a shaped charge liner and a method of manufacturing shaped charge liners which overcome the foregoing and other difficulties long since associated with the prior art. In accordance with the broader aspects of the invention, a shaped charge liner is formed from an alloy of copper, nickel, and tin. The alloy is first formed into a powder which is pressed into the form of a strip and then sintered. The strip may be cold rolled after sintering. Next, the strip is formed into the desired liner shape, for example, stamping, spinning, and other well known metal working techniques may be used to form the strip into the desired liner shape.
In actual practice, it has been found that liners formed in accordance with the invention do not form slugs when utilized in otherwise conventional shaped charge applications. Thus, the present invention provides a shaped charge liner which provides superior performance.